We picked up these today (and more, soon to come) on a Collectors Weekly field trip/scavenger hunt of sorts.

As the top label says, these are silver nickels from World War II (1942 through 1945, to be precise). Nickel was a relatively scarce metal at the time, needed for the war, so the government started minting them out of a silver alloy instead (silver, copper, and manganese). (Normally, they are 75% copper and 25% nickel.) As you can tell, some are in better condition than others in this set.

The letters below each coin correspond to where they were minted, as follows:
D: Denver
P: Philadelphia
S: San Francisco

These letters appear on the back of each nickels, over Monticello (sorry if this is old hat for all of you coin collectors out there---I'm just learning some of this stuff for the first time!).